1. Field of the Invention
The invention relates to a system for winding a cone within a machine which supplies filamentary material (such as yarn or the like) to the cone at a constant speed. Preferred embodiments of the invention are directed toward a system for winding a cone around a bobbin or spool within one of a plurality of winding stations of a textile machine which supplies yarn to the cone at a constant speed.
2. Description of Related Art
Systems have been developed for winding a cone within a textile machine which supplies yarn at a constant speed. All such systems attempt to eliminate the inherent shifting of what is known as the "pure rolling point." The "pure rolling point" is the point on a common surface line between a cylindrical drive member and the cone at which the circumferential velocity of the cone is equal to the circumferential velocity of the drive member. There is no slippage between the drive member and the cone at the pure rolling point. However, slippage generally occurs along the common surface line on each side of the pure rolling point because of the different geometries of the cone and the cylindrical drive member.
A known system for winding a cone includes a drive member formed of three side-by-side rollers on a shaft. The central roller is driven by the shaft. The cone is driven exclusively by the central roller. The lateral rollers are free to turn with respect to the shaft. In spite of its simple design and advantages, this system is unsatisfactory because it cannot maintain a desired winding velocity throughout the entire winding process. Maintenance of such a desired winding velocity is important, particularly when winding a cone within an open-end spinning machine which supplies yarn at a constant speed.
In an improvement, the lateral rollers are connected to each other through a differential gear (EP 0 063 690). In this system, torque is transmitted to the cone along its entire length. Differences in circumferential velocities along the length of the cone are compensated for by the differential gear. However, even in this improved system, the pure rolling point moves along the face of the cone during winding as yarn traverses from one end of the cone to the other. This causes deviations from the desired winding velocity. Such deviations cannot be reliably compensated for. The improved system further produces poorly structured cones. Yarn loosening frequently occurs during an initial phase in which yarn is wound onto an empty tube. The differential gear does not function properly during this initial phase. Such yarn loosening may cause yarn rupture. Then, as a consequence of changes in pressure, cone hardness, and other rolling conditions, tension in the yarn drops as winding proceeds.
Other known systems attempt to solve the problems of the prior art by improving friction properties in the vicinity of the pure rolling point. However, these systems cannot eliminate displacement (or shifting) of the pure rolling point. Accordingly, these systems must be combined with other measures (such as active modification of tension within the system).
One such system (OS 262 970) features a friction zone created on a drive roller which is fixed to a drive shaft with other supporting rollers adapted to rotate freely with respect to the drive shaft. This controls the friction between the cone and the drive roller and controls displacement of the pure rolling point. Nevertheless, tension within the winding zone still fluctuates considerably during winding.
Still another known device (OS 249 338) has a roller which is fitted with an axially-movable friction ring. This system attempts to maintain the desired winding velocity by displacing the pure rolling point. However, since the roller is not divided, displacement is great, and the requirements connected with elimination of such displacement are considerable. Furthermore, the speed of the cone cannot be adequately controlled. A simple yarn intrusion behind a carrier plate, for instance, is sufficient to increase cone resistance against rotation and reduce winding velocity. Similar consequences result from untrue running of the carrier plate, tube distortion, insufficient torsional rigidity of the bobbin frame, cone vibrations, etc. The system does not keep yarn tension within required limits and has not been accepted by the industry.
To compensate for differences in fiber length, it has been proposed to drive the cone with a variable angular velocity. In this system, instead of being driven by a roller, the cone is moved parallel to its curved surface by reciprocating the driving member along the cone as illustrated in FIGS. 3 and 4 of DE-OS 2 58 853. However, this reciprocating motion causes heavy wear of the yarn. The strain increases as the amount of yarn on the cone increases because the driving member presses harder on the cone windings as the weight of the cone increases. The resulting damage makes the system unusable at high pressures. Furthermore, drive transmission efficiency is poor because of the small width of the driving member. Slippage does not permit adjustment of velocity.
In another system, displacement of the point at which the cone is driven is achieved by a plurality of supporting rollers for selectively driving the cone. This requires the driving roller to be axially displaceable within a stroke reaching from a first supporting roller at one end of the cone to a supporting roller at the other end of the cone. This large stroke exposes the driving roller to considerable wear. Further, the velocity at which the cone is driven can be changed only in discrete increments corresponding in number to the number of supporting rollers. If this number is small, the drive transmission area is very small and consequently transmission efficiency is poor.
Furthermore, the above-described systems do not take into account filament tension. Without such control, cones are wound unevenly.
Another known system (DE-PS 1 912 374) has partial rollers which are selectively connectable with a drive shaft by clutches. The clutches are controlled by a swinging arm over which the yarn is led in a loop. Dimensional changes in the loop modify the circumferential velocity of the cone. In this system, the adjustment of cone grooves to changes in yarn tension is rather rough because the total number of clutches is restricted.
Another known system (OS 255 131) has a friction clutch for disengaging a driving roller from a drive shaft upon yarn rupture and/or diminishing of the compensation length of the yarn. The drawback of this system is that the cone is driven by a single, wide member so that regulation of the pure rolling point is poor and a constant cone drive cannot be obtained.
In another known system (EP 0 165 511), a change in yarn tension in the winding zone is registered by a sensor which cooperates with a drive system. The drive system appropriately modifies the transmission ratio of an adjustable transmission gear for transmitting motion from a central drive to the cone.
The drawback of this system is the necessity of a transmission gear and a drive for each winding unit. More importantly, continuous regulation of the whole system is not possible. When there is a change in velocity ratio, it takes time (depending on the velocity of the drive system) to displace a transmission member on bevel gears. Therefore, correction of yarn tension changes beyond the permitted range occurs only by changing the velocity ratio in the transmission gear. In the meantime, the yarn tension could undergo another change calling for another modification of the velocity ratio. Due to the step-like character of the braking and starting of the rotary members of the driving roller and the resulting inertial effects, considerable fluctuation in yarn tension occurs. As a result, the quality of the completed cone and the quality of the yarn within the cone are poor.